Experimental and computational investigation of structure and magnetism in pyrite Co1-xFexS2:: Chemical bonding and half-metallicity -: art. no. 214409

Bulk samples of the pyrite chalcogenide solid solutions Co1-xFexS2 (0less than or equal toxless than or equal to0.5), have been prepared and their crystal structures and magnetic properties studied by x-ray diffraction and SQUID magnetization measurements. Across the solution series, the distance between sulfur atoms in the persulfide (S-2(2-)) unit remains nearly constant. First principles electronic structure calculations using experimental crystal structures as inputs point to the importance of this constant S-S distance, in helping antibonding S-S levels pin the Fermi energy. In contrast hypothetical rock-salt CoS is not a good half metal, despite being nearly isostructural and isoelectronic. We use our understanding of the Co1-xFexS2 system to make some prescriptions for new half-metallic ferromagnetic.